Trait-based initialization and other utilities

Adds the concept of a 'platform', a centralized place in which
environment-specific information will be managed, and provides common
initialization logic for most "standard" apps.

As part of the common initialization, other parts of core have also
been reworked:

- HTTP-related unmarshallers and path matchers have been factored out
  from core.json to a new core.rest.directives package (core.json
  extends those unmarshallers and matchers for backwards
  compatibility)

- CORS handling has also been moved to a dedicated utility trait

- Some custom headers have been moved from raw headers to typed ones
  in core.rest.headers

- The concept of a "reporter" has been introduced. A reporter is a
  context-aware combination of tracing and logging. It is intended to
  issue diagnostic messages that can be traced across service
  boundaries.

Closes #192
Closes #195

1 files changed, 40 insertions, 0 deletions

diff --git a/src/main/scala/xyz/driver/core/rest/directives/Unmarshallers.scala b/src/main/scala/xyz/driver/core/rest/directives/Unmarshallers.scala
new file mode 100644
index 0000000..6c45d15
--- /dev/null
+++ b/src/main/scala/xyz/driver/core/rest/directives/Unmarshallers.scala
@@ -0,0 +1,40 @@
+package xyz.driver.core
+package rest
+package directives
+
+import java.util.UUID
+
+import akka.http.scaladsl.marshalling.{Marshaller, Marshalling}
+import akka.http.scaladsl.unmarshalling.Unmarshaller
+import spray.json.{JsString, JsValue, JsonParser, JsonReader, JsonWriter}
+
+/** Akka-HTTP unmarshallers for custom core types. */
+trait Unmarshallers {
+
+  implicit def idUnmarshaller[A]: Unmarshaller[String, Id[A]] =
+    Unmarshaller.strict[String, Id[A]] { str =>
+      Id[A](UUID.fromString(str).toString)
+    }
+
+  implicit def paramUnmarshaller[T](implicit reader: JsonReader[T]): Unmarshaller[String, T] =
+    Unmarshaller.firstOf(
+      Unmarshaller.strict((JsString(_: String)) andThen reader.read),
+      stringToValueUnmarshaller[T]
+    )
+
+  implicit def revisionFromStringUnmarshaller[T]: Unmarshaller[String, Revision[T]] =
+    Unmarshaller.strict[String, Revision[T]](Revision[T])
+
+  val jsValueToStringMarshaller: Marshaller[JsValue, String] =
+    Marshaller.strict[JsValue, String](value => Marshalling.Opaque[String](() => value.compactPrint))
+
+  def valueToStringMarshaller[T](implicit jsonFormat: JsonWriter[T]): Marshaller[T, String] =
+    jsValueToStringMarshaller.compose[T](jsonFormat.write)
+
+  val stringToJsValueUnmarshaller: Unmarshaller[String, JsValue] =
+    Unmarshaller.strict[String, JsValue](value => JsonParser(value))
+
+  def stringToValueUnmarshaller[T](implicit jsonFormat: JsonReader[T]): Unmarshaller[String, T] =
+    stringToJsValueUnmarshaller.map[T](jsonFormat.read)
+
+}